1. Field of the Invention
The present invention relates to a linear guide apparatus constituted by a guide rail, a slider and a plurality of rolling elements.
2. Description of the Related Art
FIG. 7 shows a example of the linear guide apparatus according to the related art. As shown in the drawing, a linear guide apparatus is constituted by a guide rail 1, a slider 2, which is also referred to as “bearing”, and a plurality of ball 3 as a rolling element.
The guide rail 1 includes rolling grooves 11 extended in axial direction and formed at both side surfaces thereof. The slider 2 has leg portions 2A arranged on both sides in a width direction of the guide rail 1, and a horizontal portion 2B connecting the leg portions 2A each other. The horizontal portion 2B is arranged on one end side (i.e., upper face side of the guide rail 1 in the drawing) in a thickness direction of the guide rail 1, that is a direction orthogonal to both of a length direction and a width direction. Further, two inner side faces of the slider 2 are arranged at two side faces of the guide rail 1 so as to be opposed each other.
The slider 2 is divided into a main body 21 and end caps 22 in a guiding direction, and the end caps 22 are arranged at the both ends in the guiding direction of the main body 21. Further, two inner side faces of the main body 21 are formed with rolling grooves 21a opposed to the rolling grooves 11 of the guide rail 1 respectively. A rolling passage 12 of the balls 3 is formed by the rolling grooves 11, 21a. 
A return passage 21b in a linear shape is formed on an outer side of the rolling groove 21a of the main body 21 of the slider 2. Direction changing passages 22a in a shape of a semicircular arc are formed at the portions of the end cap 22 arranged at two side faces of the guide rail 1. The rolling passage 12 and the return passage 21b are communicated by the direction changing passage 22a. A circulating passage 25 for infinitely circulating the balls 5 is constituted by the respective passages.
The linear guide apparatus is provided with four pieces that are two pairs and four rows of the circulating passages and the slider 2 slides along the guide rail 1 by rolling the balls 3 at the respective circulating passages 25.
Although according to the linear guide apparatus of the related art, the return passage 21b is formed by boring the main body 11 made of a metal, the operation takes time, labor and cost.
As a method of substituting the above-mentioned fabricating method, in Japanese Utility Model Unexamined Publication JP-UM-A-61-85716, there is described a method of providing a recessed groove on an outer side of a leg portion of a slider, covering the recessed groove by a closing member and fixing both ends in a length direction of the closing member by the end caps According to the method, a return passage is constituted by the recessed groove and an inner face of the closing member.
However, according to the method described in the JP-UM-A-61-85716, a number of parts are increased and integration is complicated more than the method of boring the main body made of a metal. Further, when the closing member is insufficiently fixed, there is a case in which the part is vibrated and noise is emitted.
Further, Japanese Patent Examined Publication JP-B-2846050 describes that a slider is divided into a block made of a metal, a square ring member made of a synthetic resin and a pair of plates made of a synthetic resin. In a width direction of the slider, each of two leg portions of the slider is divided into the block and the square ring member or the plate. Further, in a thickness direction of the slider, each of the leg portions at outer side portions in the width direction is divided in two of the square ring member and the plate. Further, grooves are provided on the square ring member and the plate in the thickness direction so as to form a return passage and a direction changing passage.
According to the slider described in the JP-B-2846050, the direction changing passage is constituted by the groove divided in two in the thickness direction. Therefore, also a scoop portion which is referred to as tongue for directing a rolling element from a rolling groove to the direction changing passage, or vice versa, is constituted by a member, divided in two in the thickness direction. Accordingly, strength of the tongue is deteriorated in comparison with the case in which the scoop portion comprises an undivided member.
As a proposal capable of resolving the problem, Japanese Patent Unexamined Publication JP-A-7-317762 describes that there is formed a slider in which a return passage is constituted by an undivided member by integrally molding at least a portion on an outer side in a width direction of a leg portion that is a portion formed with the return passage to a block member as a mold member comprising synthetic resin.
However, according to the slider described in the JP-A-7-317762, the mold member having the outer side portion in the width direction of the leg portion is fixed to the block member by integral molding. Therefore, it is difficult to modify the slider after molding. Further, because a structure of a die of integral molding is complicated, there is a room for improvement also in view of productivity.
That is, according to the slider described in JP-A-7-317762, because the resin continuously covers the slider, modifications including a modification of a groove depth, a shape or the like of the rolling groove cannot be carried out at all after molding. Therefore, the resin must be destructed when adjustment of pre-pressure is required or an improvement in operability is required. Further, the resin flows in a thin-walled state at a surrounding the slider, particularly, because the resin is made to flow elongated along the longitudinal direction to the slider, the molding performance is poor and a structure of the die becomes complicated. Further, a step of cooling the slider after molding by putting the slider into the die is needed and therefore, time is taken for fabrication.
There are pointed out that the linear guide apparatuses described in Japanese Patent Examined Publications JP-B-2936166 and JP-B-3182134, as the example of linear guide apparatus which include a slider in which a return passage of a rolling element is constituted by an undivided member and in which productivity of the slider is higher than that of the JP-A-7-317762.
The JP-B-2936166 and JP-B-3182134 describe that an outer side portion in a width direction of a leg portion of the slider that is a portion formed with return passage is constituted by a mold member comprising a synthetic resin and the outer side portion is separate from a block member made of a metal.
According to the linear guide apparatus of the JP-B-2936166, the slider is constituted by a main body of a metal, a frame member made of a synthetic resin including a portion formed with a return passage, and a turning plate made of a synthetic resin including an outer groove of a direction changing passage. The frame member includes an end plate provided on an outer side in a guiding direction in respect to the turning plate. The turning plate is arranged between the end plate and the main body in the guiding direction. Further, the turning plate includes a projection fitted to a recessed portion of an upper face of the main body. The projection is fitted to the recessed portion of the side plate of the frame member. That is, respective members are connected by the projection and the recessed portion which receives the projection.
According to the linear guide apparatus of the JP-B-3182134, the slider is constituted by a main body made of a metal, a pair of left and right side frames made of a synthetic resin including a portion formed with a return passage, and an end cap made of synthetic resin including an outer groove of a direction changing passage. The members are connected by a dowel, mortise joint or snapping means.
Further, Japanese Patent Unexamined Publication JP-A-13-248637 describes that a return passage of the slider is formed by inserting a pipe into a through hole formed at a position of the return passage, a slit is provided at the pipe to constitute an oil groove, and a felt is fixed to an inner peripheral surface of the pipe to impregnate a lubricant.
In the JP-B-2936166, the members having passages which form a circulation passage of the rolling elements are connected each other by engaging the protrusion portion with the recessed portion. However, because the members are not connected firmly relative to the members which are made of undivided member, it tends to occur vibration when the rolling elements roll in the circulation passage.
Further, in the JP-B-3182134, the side frames on which the return passages are formed and the end cap on which the direction changing passage is formed are made separately, and these members are connected each other by snapping means. However, because the return passage and the direction changing passage are not connected firmly relative to the members which are made of undivided member, it tends to occur vibration when the rolling element rolls between the return passage and the direction changing passage. Even a small manufacturing error of the snapping means way occur the vibrations. Therefore, there is a room of improvement in view of vibration in the linear guide apparatus described in the above-mentioned cases.